package 第12周_AVL树和红黑树;

import org.w3c.dom.Node;
import 第8周_二分搜索树.集合与映射.Map.BSTMap;

import java.time.temporal.ValueRange;
import java.util.ArrayList;

public class AVLTree<K extends Comparable<K>, V> {

    private class Node{
        public K key;
        public V value;
        public Node left, right;
        public int height;

        public Node(K key, V value){
            this.key = key;
            this.value = value;
            left = null;
            right = null;
            height = 1;
        }
    }

    private Node root;
    private int size;

    public AVLTree(){
        root = null;
        size = 0;
    }

    public int getSize(){
        return size;
    }

    public boolean isEmpty(){
        return size == 0;
    }

    /**
     * 判断该二叉树是否是一颗二分搜索树
     * @return
     */
    public boolean isBST(){
        ArrayList<K> keys = new ArrayList<>();
        inOrder(root, keys);
        for (int i = 0; i < keys.size(); i++) {
            if (keys.get(i - 1).compareTo(keys.get(i)) > 0){
                return false;
            }
        }
        return true;
    }

    /**
     * 中序遍历
     * @param node
     * @param keys
     */
    private void inOrder(Node node, ArrayList<K> keys){
        if (node == null){
            return;
        }

        inOrder(node.left, keys);
        keys.add(node.key);
        inOrder(node.right, keys);
    }

    /**
     * 判断该二叉树是否是一颗平衡二叉树
     * @return
     */
    public boolean isBalanced(){
        return isBalanced(root);
    }

    /**
     * 判断以node 为根的二叉树是否是一颗平衡二叉树
     * @param node
     * @return
     */
    private boolean isBalanced(Node node){
        if (node == null){
            return true;
        }

        int balanceFactor = getBalanceFactor(node);
        if (Math.abs(balanceFactor) > 1){
            return false;
        }
        return isBalanced(node.left) && isBalanced(node.right);
    }


    /**
     * 获得节点node的高度
     * @param node
     * @return
     */
    private int getHeight(Node node){
        if (node == null){
            return 0;
        }
        return node.height;
    }

    /**
     * 获得节点node 的平衡因子
     * @param node
     * @return
     */
    private int getBalanceFactor(Node node){
        if (node == null){
            return 0;
        }
        return getHeight(node.left) - getHeight(node.right);
    }

    /**
     * 对接点进行右旋转， 返回旋转后新的跟节点
     * @param y
     * @return
     */
    private Node rightRotate(Node y){
        Node x = y.left;
        Node T3 = x.right;

        //向右旋转过程
        x.right = y;
        y.left = T3;

        //更新height
        y.height = Math.max(getHeight(y.left), getHeight(y.right)) + 1;
        x.height = Math.max(getHeight(x.left), getHeight(x.right)) + 1;

        return x;
    }

    /**
     * 左旋转
     * @param y
     * @return
     */
    private Node leftRotate(Node y){
        Node x = y.right;
        Node T2 = x.left;

        //向左旋转过程
        x.left = y;
        y.right = T2;

        //更新height
        y.height = Math.max(getHeight(y.left), getHeight(y.right)) + 1;
        x.height = Math.max(getHeight(x.left), getHeight(x.right)) + 1;
        return x;
    }


    /**
     * 向AVL树中添加元素
     * @param key
     * @param value
     */
    public void add(K key, V value){
        root = add(root, key, value);
    }

    private Node add(Node node, K key, V value){
        if (node == null){
            size++;
            return new Node(key, value);
        }

        if (key.compareTo(node.key) < 0){
            node.left = add(node.left, key, value);
        }else if (key.compareTo(node.key) > 0){
            node.right = add(node.right, key, value);
        }else{
            node.value = value;
        }

        //更新height
        node.height = 1 + Math.max(getHeight(node.left), getHeight(node.right));

        //计算平衡因子
        int balanceFactor = getBalanceFactor(node);
        if (Math.abs(balanceFactor) > 1){
//            System.out.println("unbalanced :" + balanceFactor);
        }

        //平衡维护  向左倾斜
        //LL
        if (balanceFactor > 1 && getBalanceFactor(node.left) >= 0){
            //右旋转
            return rightRotate(node);
        }

        //向右倾斜
        //RR
        if (balanceFactor < -1 && getBalanceFactor(node.right) <= 0){
            //左旋转
            return leftRotate(node);
        }

        //LR
        if (balanceFactor > 1 && getBalanceFactor(node.left) < 0){
            node.left = leftRotate(node.left);
            return rightRotate(node);
        }

        //RL
        if (balanceFactor < -1 && getBalanceFactor(node.right) > 0){
            node.right = rightRotate(node.right);
            return leftRotate(node);
        }
        return node;
    }

    /**
     * 返回以node为根节点的二分搜索树中，key所在的节点
     * @param node
     * @param key
     * @return
     */
    private Node getNode(Node node, K key){
        if (node == null){
            return null;
        }

        if (key.compareTo(node.key) == 0){
            return node;
        }else if (key.compareTo(node.key) < 0){
            return getNode(node.left, key);
        }else{
            return getNode(node.right, key);
        }
    }

    public boolean contains(K key){
        return getNode(root, key) != null;
    }

    public V get(K key){
        Node node = getNode(root, key);
        return node == null ? null : node.value;
    }

    public void set(K key, V newValue){
        Node node =  getNode(root, key);
        if (node == null){
            throw new IllegalArgumentException("这个键不存在");
        }
        node.value = newValue;
    }

    /**
     * 返回以node为根的二分搜索树的最小值所在的节点
     * @param node
     * @return
     */
    private Node Minimum(Node node){
        if (node.left == null){
            return node;
        }
        return Minimum(node.left);
    }

    public Node removeMin(Node node){
        if (node.left == null){
            Node rightNode = node.right;
            node.right = null;
            size--;
            return rightNode;
        }

        node.left = removeMin(node.left);
        return node;
    }

    /**
     * 从二分搜索树中删除键为key的节点
     * @param key
     * @return
     */
    public V remove(K key){
        Node node = getNode(root, key);
        if (node != null){
            root = remove(root, key);
            return node.value;
        }
        return null;
    }

    private Node remove(Node node, K key){
        if (node == null){
            return null;
        }

        //最终要返回的根节点
        Node retNode;
        if (key.compareTo(node.key) < 0){
            node.left = remove(node.left, key);
            retNode =  node;
        }
        else if (key.compareTo(node.key) > 0){
            node.right = remove(node.right, key);
            retNode =  node;
        }
        else {
            //待删除的节点左子树为空的情况
            if (node.left == null){
                Node rightNode = node.right;
                node.right = null;
                size--;
                retNode =  rightNode;
            }
            //待删除的节点为右子树的情况
            else if (node.right == null){
                Node leftNode = node.left;
                node.left = null;
                size--;
                retNode =  leftNode;
            }else {
                //待删除的节点左右子树皆不为空
                //找到比待删除节点大的最小节点，即待删除节点右子树的最小节点
                //用这个节点顶替待删除节点的位置
                Node successor = Minimum(node.right);
                successor.right = remove(node.right, successor.key);  //removeMin(node.right);
                successor.left = node.left;
                node.left = node.right = null;
                retNode =  successor;
            }
        }

        //防止空指针异常
        if (retNode == null){
            return null;
        }

        //更新height
        retNode.height = 1 + Math.max(getHeight(retNode.left), getHeight(retNode.right));

        //计算平衡因子
        int balanceFactor = getBalanceFactor(retNode);
        if (Math.abs(balanceFactor) > 1){
            System.out.println("unbalanced :" + balanceFactor);
        }

        //平衡维护  向左倾斜
        //LL
        if (balanceFactor > 1 && getBalanceFactor(retNode.left) >= 0){
            //右旋转
            return rightRotate(retNode);
        }

        //向右倾斜
        //RR
        if (balanceFactor < -1 && getBalanceFactor(retNode.right) <= 0){
            //左旋转
            return leftRotate(retNode);
        }

        //LR
        if (balanceFactor > 1 && getBalanceFactor(retNode.left) < 0){
            node.left = leftRotate(retNode.left);
            return rightRotate(retNode);
        }

        //RL
        if (balanceFactor < -1 && getBalanceFactor(retNode.right) > 0){
            node.right = rightRotate(retNode.right);
            return leftRotate(retNode);
        }

        return retNode;
    }


}
